1. Field of the Invention
The present invention relates to a dither matrix generating method, an image processing device, and a non-transitory computer readable storage medium storing a program.
2. Description of the Related Art
In a printing device that prints an image by forming dots on a printing medium, since a number of available gradation values for a dot is limited relative to a number of gradation values which can be input, gradation is expressed by halftone processing.
As an example of the halftone processing, a dithering method can be considered. In the dithering method, a halftone is reproduced by a combination of density gradation (intensity modulation) and area gradation (area modulation), for which a number of levels is fewer than that of the original (cf. Patent Document 1 (Japanese Unexamined Patent Publication No. 2003-152999), for example).
A concentration type dither matrix is often used in halftone processing, for which a dither method according to related art is applied. The concentration type dither matrix is often used because it demonstrates good dot reproducibility and high image quality. However, when the concentration type dither matrix is utilized in a low density portion, a gap tends to be generated between neighboring dots, and a fine line tends to be broken. In this regard, by using distributed dithering or non-periodic dithering, breaking of a fine line has been reduced.
However, an effect of reducing breaking of a fine line is not so strong for the distributed dithering. In addition, the distributed dithering may cause a color shift, for example, and may lower image quality. For the non-periodic dithering, a size of a matrix may be increased. Accordingly, printing speed may be reduced, and cost may be increased due to an increase of required memory capacity.
An embodiment of the present invention has been developed in view of the above-described problems. It is desirable to provide a dither matrix generating method, which can reduce breaking of a fine line and which can enhance image quality. It is also desirable to provide an image processing method; an image processing device; and a program, in which the above-described dither matrix is utilized.